title: Age-specific incidence of A/H1N1 2009 influenza infection in England from sequential antibody prevalence data using likelihood-based estimation.
abstract: Estimating the age-specific incidence of an emerging pathogen is essential for understanding its severity and transmission dynamics. This paper describes a statistical method that uses likelihoods to estimate incidence from sequential serological data. The method requires information on seroconversion intervals and allows integration of information on the temporal distribution of cases from clinical surveillance. Among a family of candidate incidences, a likelihood function is derived by reconstructing the change in seroprevalence from seroconversion following infection and comparing it with the observed sequence of positivity among the samples. This method is applied to derive the cumulative and weekly incidence of A/H1N1 pandemic influenza in England during the second wave using sera taken between September 2009 and February 2010 in four age groups (1-4, 5-14, 15-24, 25-44 years). The highest cumulative incidence was in 5-14 year olds (59%, 95% credible interval (CI): 52%, 68%) followed by 1-4 year olds (49%, 95% CI: 38%, 61%), rates 20 and 40 times higher respectively than estimated from clinical surveillance. The method provides a more accurate and continuous measure of incidence than achieved by comparing prevalence in samples grouped by time period.
authors.affiliation: Immunisation, Hepatitis and Blood Safety Department, Health Protection Agency, London, United Kingdom. marc.baguelin@hpa.org.uk
authors.forename: Marc
authors.initials: M
authors.lastname: Baguelin
authors.forename: Katja
authors.initials: K
authors.lastname: Hoschler
authors.forename: Elaine
authors.initials: E
authors.lastname: Stanford
authors.forename: Pauline
authors.initials: P
authors.lastname: Waight
authors.forename: Pia
authors.initials: P
authors.lastname: Hardelid
authors.forename: Nick
authors.initials: N
authors.lastname: Andrews
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Miller
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000914:Antibodies, Viral / Q000032:analysis / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D003627:Data Interpretation, Statistical; D004196:Disease Outbreaks; D004739:England / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007251:Influenza, Human / Q000097:blood / Q000453:epidemiology* / Q000276:immunology; D016013:Likelihood Functions; D008297:Male; D015995:Prevalence; D016036:Seroepidemiologic Studies; D013997:Time Factors; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral